The present invention relates to an arrangement on a packing machine of the type which manufactures filled and closed packing containers from tubular container blanks and which comprises, among other things, a stepwise rotatable mandrel wheel having a plurality of radial mandrels distributed around the mandrel wheel which are intended to move container blanks applied to the mandrels between successive processing stations so as to achieve a bottom closure of the blanks. More particularly the invention relates to an arrangement of the type which comprises clamping elements pressed against the mandrels for the retaining of the container blanks in a previously determined correct position on the mandrels during their stepwise movement between the bottom forming stations around the mandrel wheel.
Containers of the ridge or gable-top type have been known for a long time in packing technique. They are manufactured usually from container blanks prepared beforehand which appropriately can be provided with a creaseline pattern in order to facilitate the forming of the containers through folding of the panels, representing the top and bottom closures to their final position. Frequently the blanks are coated with a thermoplastic material, e.g. polyethylene, which is used on the one hand to make the container liquid-tight and on the other hand to allow the sealing of the container by heat and pressure (so-called hot-sealing) so that it permanently retains its intended final form.
The packages described above are used primarily as packages for liquid goods, e.g. milk or similar dairy products, and over the years different machines for the manufacture of the packages have been designed. A number of these machines comprise one or more intermittently driven mandrel wheels, usually arranged in pairs, with mandrels on which the container blanks are attached and moved between different processing stations located around the mandrel wheel or wheels, so as to achieve a liquid-tight bottom closure on the blanks. In order to make it possible to provide such a closure it is necessary not only that the container blanks should be applied to the mandrels in a correctly adapted position with regard to the actual crease line pattern, but also that the blanks so applied should be maintained in this position during the movement between the bottom-forming operations. Accordingly any radial displacements, which may be caused for example by the pressing forces acting upon the container blanks during hot-sealing, ought to be counter-acted as long as possible or preferably prevented. On certain known packing machines such a position fixing of the blanks is provided with the help of so-called mandrel stops in the form of a stop dog or stop element, manually displaceable along a radial sliding groove in the mandrels and lockable in optional positions, which defines the correct furnishing length for the blanks.
One disadvantage of these known mandrel stops is of course that on resetting of the machine from one package size (container length) to another it is necessary to individually readjust all of the stop dogs. This is very time-consuming process and involves unnecessarily lengthy machine stoppages and, consequently, large production losses. Furthermore, mandrels provided with sliding grooves are relatively difficult to keep clean of dirt, and debris which tends to accumulate and deposit in the kind of recesses which such grooves.
It is an object of the present invention, therefore, to overcome these disadvantages of the known technique regarding mandrel stops.
This object is achieved in accordance with the invention in that a position-fixing arrangement for container blanks on a packing machine of the type described above has the clamping elements being moveable with the help of stops at one or more of the processing stations for at least a partial disengagement of the clamping elements from the container blanks.
The invention together with advantageous practical details for realization of the same will be explained in greater detail in the following with reference to the attached drawings on which: